What is included with DDP...I assume meal and drink? It says 18% service charge added...so we pay that like a tip? If we were to order it for Xmas morning, before our flight home, what amount of time should I allow? Our flight is 10:20 and I assume we'll get on the ME around 7:00-7:20. I'd like the food delivered around 6:00-ish...what time should I order?

That menu says you need to order a minimum of 24 hours in advance. So 6 AM exactly the day before, if not the evening before that. Also, you need to be ready/waiting for your Magical Express bus 15 minutes before your assigned time, as that's when it leaves your resort. Add extra time if you're also using RAC.